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Yadkin
12-06-2016, 01:25 PM
I'm at the consideration stage of another modification for my '64. The most popular OD addition seems to be a product by Gear Vendors that bolts in place of my existing tailshaft. http://www.gearvendors.com/hrford3s.html

With my existing 225/70/15 tires and 3.00 differential I'm turning:
2200 RPM at 60 mph
2400 RPM at 65
2600 RPM at 70.

The Gear Vendors unit has a .714 ratio so this would be reduced. The third column is my estimated torque based on OE specs:
1600 RPM at 60 ; 300#-ft
1700 RPM at 65; 325 #-ft
1800 RPM at 70; 350 #-ft

My daily driver, a '12 Jeep Grand Cherokee, I figure weighs about 400# more than the TBird. For comparison:
1700 RPM at 60 ; 260#-ft
1800 RPM at 65; 260 #-ft
2000 RPM at 70; 260 #-ft

So this should work well. I'd like to know what others have done.

simplyconnected
12-06-2016, 08:01 PM
1,800-RPM sounds wonderful at 70-MPH but where does that fall in the torque range of your cam???

If you're at the lower end of the spectrum, you're not taking advantage of peak torque. I would want to see my engine running around 2,500 (or more) at 70-MPH. You are leaving the good stuff at speeds you rarely use. - Dave

OX1
12-07-2016, 10:13 AM
1,800-RPM sounds wonderful at 70-MPH but where does that fall in the torque range of your cam???

If you're at the lower end of the spectrum, you're not taking advantage of peak torque. I would want to see my engine running around 2,500 (or more) at 70-MPH. You are leaving the good stuff at speeds you rarely use. - Dave

More important than that, what is your terrain, elevation, etc...

I can get away with a stock 2bbl 302 (with 4bbl added), 33 tires, T-18 4 speed
stock 3.5 gear (15%ish overdrive compared to stock gears/tires), and 60 MPH on flat ground @ sea level
on my early bronco (absolute brick aerodynamically, even compared to SB), but the guy in
the Tenesee Mnts tells me I'm nuts for running this setup.

We have that disagreement all the time on message boards, since everyone's
terrain/expectations are highly different.

pbf777
12-07-2016, 11:07 AM
Speaking in very general terms of use, one would not require, or seemingly benefit greatly, with the expense and installation of an overdrive unit, in the scenario as you have outlined.

The considerations you present are: 1964 T-Bird, although not a light-weight, it also is not the worst automobile aerodynamically (@60-70 M.P.H.), therefore not relatively high loads to push at these speeds.

Also, the 3.00:1 axle ratio & tire size resulting in the R.P.M. values your list when coupled to the O.D. unit may be a bit slow, depending on the speed in which you travel of course. At the relatively low load presented at cruising speeds the peak torque values are not so relevant, but if the engine R.P.M.s fall too low, or as we sometimes term "under-the-cam" then inefficiencies within the induction & exhaust may overcome the savings in R.P.M. reduction.

Generally, the overdrive units are utilized when one is applying more axle gear multiplication then you present; which may also be a consideration here. Keep in mind, your particular driving style and environment has as much to due with the appropriate component choice as the math. Scott.

simplyconnected
12-07-2016, 11:52 AM
More important than that, what is your terrain, elevation, etc...Exactly! That's why you want to cruise in that torque curve, especially in mountains. We call that the 'service' your engine is built for.

Steve has already experienced driving outside the torque curve and it compelled him to change his cam grind. Now it's transmission ratios.

This is typical, everyone wants big power but when they get it at high RPMs they miss having torque at low end and fuel efficiency. You can't have it both ways. Edelbrock heads have intake valves so large the heads won't fit a 352 because they hit the cylinder walls. But a low RPM mill creates much more low end torque with small valves, like pickup trucks come with.

I guess the bottom line is this:
Know what service you really want BEFORE the rebuild, then the driveline can easily be matched. What are the choices? Compression ratios, cam grind, heads, torque converter, transmission ratios, rear end gears and tires. All these factors play important roles in the type of service your car will live in. All the rest; carb or EFI, cam timing, exhaust system, distributor curve, shift kit, etc., are all 'tuning' aids.

Car manufacturers are experts. They hire the finest driveline engineers and they have over 100 years of experience. OEMs supply the best combination packages for all types of street service. Before you depart from stock, consult a builder who knows the correct service combination or you will end up with very expensive mis-matched parts that don't work well together. Not everyone races so a 'racing team' shop may NOT offer good advice for engine efficiency and longevity in a daily driver. - Dave

Yadkin
12-08-2016, 05:45 PM
My cam grind is for low RPM grunt. Although it's a roller, I assumed the torque values at RPM from a factory motor.

When I drive this car on 421 from Wilkesboro up to the Blue Ridge Parkway, there is a long, steep climb, much of it 8 to 10% grade. The car is very happy in 3rd gear at the posted speed limit and above. In my Jeep, 4 speed plus OD, it typically downshifts twice, into third. With the TBird, I'd expect to drop out of OD into 3rd.

My desire for an OD is for flat and rolling terrain at 65 and above.

DKheld
12-09-2016, 08:46 AM
X2 on the OD.

Irregardless of whether or not the engine would be in the correct power band etc I make a 125 mile interstate trip in mine often. The speed limit is 70 so most of the time I'm traveling about 80 (ish) to keep up with traffic.

Got to be turning 3000+ rpm.

If I could drop that RPM in half and only come in and out of OD for the occasional hill etc that would be exceptional. I'd never get my return on investment with gas mileage but couldn't beat it for interior noise reduction and just a better feel that you're not running the engine at higher revs. As a kid we made many trips to Fla in our Tbird and it lasted just fine so know they are capable of the higher revs for extended periods - just like the lower revs of a modern OD engine I guess.

Steve - I haven't researched - how is the OD engaged - vac module? electric switch? cable?
Eric

Yadkin
12-10-2016, 10:09 PM
The type I'm looking at is electric shift with automatic clutch, and has about a 28% reduction ratio. The manufacturer claims that it can be used concurrent with all of the transmission gears, basically making a 3 speed into a six speed. I think that's a bit impractical for a driver. My intent would be to shift into OD once I got up to speed, just like I drive my 05 Mustang.

Online reviews of the unit confirm that this is the practical use. Up shifts are supposedly good, but downshifts are reported as "clunky". The manufacturer claims shifts can be done at full power. I'm a bit concerned with operation.

No question that OD saves engine wear. Modern car engines last a lot longer than the old cars without OD. The manufacturer claims up to a 28% increase in fuel mileage and I sincerely doubt that.

Thunderherd
12-11-2016, 12:27 AM
There's a couple of things I'd check on that before I went that route. Although it sounds really good. I had an Airstream motor home with the GearVenders OD unit on it. Yes, it performed really well. Really lowered the rpm's when engaged. But. When not engaged in OD it was a 15% under drive. Might not be a problem for you, depending on your rearend gearing, could be a benefit. But mainly, and I consider this a safety issue, if you left it engaged in OD, when parked, and put the transmission in park, there was no lockup. What I mean is, place the trans in park and the motor home would roll off if you didn't engage the parking/emergency brake. And you have to be moving to change the gears in the Gear Vender unit. You can't just come to a stop and then flip your switch to change gears. For example, to shift up, leave your foot on the accelerator pedal, slightly under load, flip the switch, and GV unit doesn't change gears till you lift your foot off of gas pedal (releaving load on drive train) and then give it gas again. Same process down shifting. This may sound complicated, but it's really not after a time or two doing it. But you gotta remember to shift out of OD before parking. PS. There was a few times the unit wouldn't shift into OD because of electrical issues. No big deal there. But when OD was working, gas mileage was considerably better. Like from about 8 mpg without, to about 12 mpg or a little better with. 30 foot motor home with a 454 off brand motor in it. (454 Chevy, lol).

scumdog
12-11-2016, 12:12 PM
The type I'm looking at is electric shift with automatic clutch, and has about a 28% reduction ratio. The manufacturer claims that it can be used concurrent with all of the transmission gears, basically making a 3 speed into a six speed. I think that's a bit impractical for a driver. My intent would be to shift into OD once I got up to speed, just like I drive my 05 Mustang.

Online reviews of the unit confirm that this is the practical use. Up shifts are supposedly good, but downshifts are reported as "clunky". The manufacturer claims shifts can be done at full power. I'm a bit concerned with operation.

No question that OD saves engine wear. Modern car engines last a lot longer than the old cars without OD. The manufacturer claims up to a 28% increase in fuel mileage and I sincerely doubt that.

There's a guy I know here in NZ that runs one of those over drives (Hone?) behind the TH400 in his '49 Chev coupe, the motor is a pretty stout big block Chev - stout enough for high 9's in the 1/4.
He also gets reasonable gas mileage too.
And I have not heard of him having any issues with the o.d.

Yadkin
12-11-2016, 06:32 PM
There's a couple of things I'd check on that before I went that route. Although it sounds really good. I had an Airstream motor home with the GearVenders OD unit on it. Yes, it performed really well. Really lowered the rpm's when engaged. But. When not engaged in OD it was a 15% under drive. Might not be a problem for you, depending on your rearend gearing, could be a benefit. But mainly, and I consider this a safety issue, if you left it engaged in OD, when parked, and put the transmission in park, there was no lockup. What I mean is, place the trans in park and the motor home would roll off if you didn't engage the parking/emergency brake. And you have to be moving to change the gears in the Gear Vender unit. You can't just come to a stop and then flip your switch to change gears. For example, to shift up, leave your foot on the accelerator pedal, slightly under load, flip the switch, and GV unit doesn't change gears till you lift your foot off of gas pedal (releaving load on drive train) and then give it gas again. Same process down shifting. This may sound complicated, but it's really not after a time or two doing it. But you gotta remember to shift out of OD before parking. PS. There was a few times the unit wouldn't shift into OD because of electrical issues. No big deal there. But when OD was working, gas mileage was considerably better. Like from about 8 mpg without, to about 12 mpg or a little better with. 30 foot motor home with a 454 off brand motor in it. (454 Chevy, lol).

I believe that you are right on the underdrive, although using their numbers I calculate it at 1.06. Their website isn't clear on that at all. The Hot Rod magazine article that they link to explains it a bit better:

The Gear Vendors unit is a supplemental planetary gearbox that adapts to the output shaft of your existing transmission to provide an extra gear of 0.78:1. The initial benefit is the addition of a 22-percent overdrive in high gear...on the highway, your engine’s comfortable cruise rpm will result in a mph that’s 28 percent faster with the Gear Vendors engaged in top gear.

So my numbers in the OP are wrong, and should read:

The Gear Vendors unit has a .78 ratio so this would be reduced. The third column is my estimated torque based on OE specs:
1700 RPM at 60 ; 325#-ft
1900 RPM at 65; 350 #-ft
2000 RPM at 70; 375 #-ft

These RPM-mph ratios match very closely to my '12 Jeep. However the TBird weighs less and the engine produces more torque so the performance is going to be very good.

Yadkin
12-11-2016, 06:50 PM
There's a guy I know here in NZ that runs one of those over drives (Hone?) behind the TH400 in his '49 Chev coupe, the motor is a pretty stout big block Chev - stout enough for high 9's in the 1/4.
He also gets reasonable gas mileage too.
And I have not heard of him having any issues with the o.d.

I've seen the Hone. An old company that went under in the 80's and was restarted in 2014 based on reverse engineering a NOS unit that they found. It bolts in place of the pinion gear on the differential. http://hone-o-drive.com/product-category/overdrive-transmission/

Reading the entire site, I don't see where it is shift on the fly like the Gear Vendors unit. I'm looking for convenience, not something that I have to stop to shift into gear like my Jeep when I go into 4WD low.

After you buy the electronic shifter, the cost is $850 more.

pbf777
12-12-2016, 11:50 AM
The "Gear Vendors" unit design is based on the British Laycock overdrives beginning in the 1950s thru to the 1980s? This unit generally mounted directly to the transmission, post gearbox engaging it's output shaft. Operational engagement generally thru electric solenoid triggered via vacuum and/or switch.

The "Hone" or "Hone-O-Drive" was of U.S.A. manufacture beginning in the 1960s thru to the 1970s, and now reintroduced to the market place in the last few years. This unit generally mounted to the rear differential engaging the input pinion gear spline. Operational engagement generally thru mechanical linkage (lever & rod). We had a Hone on a 1970 Shelby GT500 w/ a "Tunnel-Port" 427 (@ 461 cu.in.), 4 spd., 4.88 gears; yes, you could shift at speed, with practice, with a clunk vs. grinding noises.

Do take a stare at the clearance in your trans-tunnel area, as the G.V. unit is gearbox, that mounts at the end of the tail shaft (C6?) and I believe the T-Bird has a rather deep shrouded tunnel. Scott.

Yadkin
12-12-2016, 01:04 PM
My transmission is a Cruise-O, not a C-6. Here's a picture of the FMX kit (which is probably the same). The adapter takes the place of the tailshaft and the new gearbox basically adds extra length to the transmission. I need to verify the tunnel clearance, but also my exhaust H-pipe may be in the way.

Notice the electronics module in the picture. This isn't re-warmed 1960's technology.

DKheld
12-13-2016, 08:34 AM
Electronics module looks like an upgrade from the good old dash mounted or shifter mounted switch for the MG Laycock units I'm familiar with but the OD unit is very similar - as in the Laycock patent must have expired when Gear Vendors came out with these things. :D

http://mgaguru.com/mgtech/gearbox/pics/mgb_d-type_od1.jpg

Yeah - wonder if the heat from the exhaust will adversely affect unit lifespan. Heat was a killer on the Laycock. On the MG's the exhaust was to the side and about a foot away from the OD unit. Maybe just add a heat shield.

stubbie
12-13-2016, 07:27 PM
I had a Triumph Dolomite Sprint 2litre overhead cam engine that had an electric overdrive on 3rd and 4th gear. Looked similar to that set up. Switch was in the top of the gear knob. Worked really well. I just looked into Dolomite's and it appears that they also used the Laycock units. They were also used in Jags and Aston Martins. You might be able to adapt one to your MX box from a Jag Steve.

pbf777
12-13-2016, 10:14 PM
My transmission is a Cruise-O, not a C-6. Here's a picture of the FMX kit (which is probably the same).

Question: Has Gear Vendors stated that their unit for the FMX (1968 & up) fits your transmission (FX?)? Note that the "Cruise-O-Matic" name was applied to several different transmissions over the years.

Notice the electronics module in the picture. This isn't re-warmed 1960's technology.

No, not the electronics (bells & whistles, or shall we say the switch), but, the mechanical assembly, well.................... Scott.

Yadkin
12-14-2016, 11:12 AM
No, not the electronics (bells & whistles, or shall we say the switch), but, the mechanical assembly, well.................... Scott.

Did you mean to ask me this question:
Has Gear Vendors stated that their unit for the FMX (1968 & up) fits your transmission (FX?)? Note that the "Cruise-O-Matic" name was applied to several different transmissions over the years.

Answer: I'm corresponding with them. They told me to measure the tailshaft to see if their standard adapter fits.

According to Wikipedia:

The new transmissions arrived for model year 1958 which coincided with the release of Ford's new FE and MEL engines. Although marketed as Cruise-O-Matic, the new transmissions were known internally as the MX (larger) and the FX (smaller).

In 1966... decided to combine the best attributes of the MX and FX transmissions and ended up with an improved version of the "X" called FMX. This transmission used the stronger MX-type rotating parts in the smaller FX style case.

https://en.wikipedia.org/wiki/Cruise-O-Matic#MX.2FFX

I think that mine is an MX.

pbf777
12-14-2016, 11:15 AM
Have you considered the Ford AOD transmission option?

I have never been impressed with its' strength (though you have not presented a scenario where I feel this is a grave concern) or shifting strategies, but it has proven popular for those applications not originally equipped with O.D.. An adapter plate is utilized to rectify the mismatch bellhousing bolt patterns (small block vs. FE). Scott.

Yadkin
12-14-2016, 11:42 AM
Considered, yes, but the GV unit should be simpler. I rebuilt my Cruise-O and it performs flawlessly. Even powder coated it black (for the iron) and aluminum, so it looks great too. So to dump it would devalue my investment.

Plus the linkage set-up would be very difficult to do.

I had the AOD in my '85 TBird and it was a good transmission. Full lock-up in all four gears so it was very efficient, and easy to downshift with an intuitive press on the accelerator pedal. My only problem with it that it would downshift into 3rd above 85 mph or so. I assume that the factory did this to limit the top speed of the car.

pbf777
12-15-2016, 11:48 AM
[QUOTE=Yadkin; I'm corresponding with them. They told me to measure the tailshaft to see if their standard adapter fits.
I think that mine is an MX.[/QUOTE]

When the manufacture sends you out with a tape measure, to determine if their product will fit (this ain't window drapes), you should realize that your "on your own" at this point.

I guess, the measurement you were to supply G.V.s is the length? If so, I agree it would be the first, easiest measurement which may indicate incompatibility. But, if this passes muster then the next obvious concern would be bolt pattern and sealing/mounting surfaces for the tailshaft housing to main case.

Maybe, before incurring money conversion, freight charges, and hassles with attempted returns of non fitting goods, one would attempt to purchase this sealing gasket (tailshaft housing to case) for each transmission (MX & FMX) and compare? After all, the MX was the "medium" case Cruise-O-Matic, and the FMX was an upgraded "smaller case" unit, in generic trans-lingo terms, as I understand. Note: this still doesn't guarantee fitment, but at least it's another early opportunity to rule it out. Scott.

Yadkin
12-15-2016, 12:59 PM
No need to order a gasket to see if the bolt pattern is the same. I'll measure centers on the bolts and confirm fitment with the manufacturer before I call and discuss details.

Yadkin
12-19-2016, 09:32 AM
Manufacturer's adapter is for 14" long tailshafts. Mine's 16-1/8".

pbf777
12-19-2016, 10:58 AM
Hone-O-Drive (a.k.a. "HONE")? Scott.